Polymorphic form of sepiapterin

ABSTRACT

Disclosed is a crystalline form of sepiapterin, a method of preparing the crystalline form, pharmaceutical compositions containing the crystalline form, and a method for treating patients with a disease associated with low intracellular BH4 levels or with dysfunction of various BH4 dependent metabolic pathways, which involves administering to the patient an effective amount of the crystalline form.

BACKGROUND OF THE INVENTION

Sepiapterin is a naturally occurring precursor of tetrahydrobiopterin (BH4), a naturally occurring essential cofactor of critical intracellular enzymes to include but not limited to phenylalanine hydroxylase (PAH) (Kaufman, 1958), tyrosine hydroxylase (TH) (Nagatsu et al, 1964), tryptophan hydroxylase (TPH) (Ichiyama et al, 1970), nitric oxide synthases (NOS) (Kwon et al, 1989), (Mayer et al, 1991) and alkylglycerol monooxygenase (AGMO) (Tietz et al, 1964). Rapid conversion of sepiapterin to BH4 favoring accumulation of BH4 occurs via a two-step reduction in the salvage pathway for BH4 synthesis (Sawabe, 2008). A synthetic form of BH4 (e.g., sapropterin dihydrochloride) is used as a therapy for diseases associated with high plasma phenylalanine, such as phenylketonuria (PKU). PKU is an inborn error of metabolism caused predominantly by mutations in the PAH gene. BH4 was also tested as a therapy for various central nervous symptoms associated with PKU and other diseases, but demonstrated limited effect, presumably due to the inability of BH4 to effectively cross the blood brain barrier (Klaiman et al, 2013; Grant et al, 2015).

Recent work has suggested that, compared with BH4, peripherally administered sepiapterin possesses greater permeability through membranes and as a result, can more readily access liver, kidney, and brain cells. It is reported that sepiapterin is rapidly converted into BH4 intracellularly via the tetrahydrobiopterin-salvage pathway, thereby elevating liver, kidney, and brain BH4 levels (Sawabe, 2008). As a result, sepiapterin may serve as a useful therapeutic for diseases associated with low intracellular BH4 levels or with dysfunction of various BH4 dependent metabolic pathways.

Sepiapterin herein is the S-enantiomer and has the formula (I):

It is known that sepiapterin has limited stability in solutions. Furthermore, certain forms of solid sepiapterin degrade under oxidative conditions even at room temperature and in the presence of light. Accordingly, there exists an unmet need for a crystalline solid form of sepiapterin.

BRIEF SUMMARY OF THE INVENTION

The invention provides a crystalline polymorph of sepiapterin herein defined as Form A. The invention also provides a method of preparing crystalline Form A of sepiapterin, pharmaceutical compositions comprising the crystalline Form A of sepiapterin, and a method of treating a patient with a disease associated with low intracellular BH4 levels or with dysfunction of various BH4 dependent metabolic pathways.

Accordingly, in an aspect, the invention features a crystalline form of sepiapterin having at least one peak at diffraction angle 2θ (°) of 4.7°±0.5, 7.4°±0.5, or 26.2°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry. In some embodiments, the crystalline form of sepiapterin has at least one peak at diffraction angle 2θ (°) of 4.7°±0.5, 7.4°±0.5, 9.5°±0.5, 11.3°±0.5, 15.6°±0.5, 16.4°±0.5, 26.2°±0.5, or 27.2°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry. In some embodiments, the crystalline form of sepiapterin has at least one peak at diffraction angle 2θ (°) of 4.7°±0.5, 7.4°±0.5, and 26.2°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry. In some embodiments, the crystalline form of sepiapterin has at least one peak at diffraction angle 2θ (°) of 4.7°±0.5, 7.4°±0.5, 9.5°±0.5, 11.3°±0.5, 15.6°±0.5, 16.4°±0.5, 26.2°±0.5, and 27.2°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry. In some embodiments, the crystalline form of sepiapterin has the X-ray powder diffraction spectrum as shown in FIG. 1.

In some embodiments, the crystalline form of sepiapterin has a loss of weight from 30° C. to 150° C. of less than 15% as measured by thermal gravimetric analysis. In some embodiments, the crystalline form of sepiapterin has an endothermic onset at about 84° C. or about 180° C. in differential scanning calorimetry (DSC) profile. In some embodiments, the crystalline form of sepiapterin has an endothermic onset at about 84° C. and about 180° C. in differential scanning calorimetry (DSC) profile. In some embodiments, the crystalline form of sepiapterin has an ¹H NMR spectrum substantially similar to the spectrum shown in FIG. 4.

In another aspect, the invention features a pharmaceutical composition comprising any of the forgoing crystalline forms of sepiapterin and a pharmaceutically acceptable carrier. In some embodiments, the crystalline form of sepiapterin is formulated as particles less than 100 μm in size.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes:

(i) combining sepiapterin free base and hydrochloric acid;

(ii) isolating the hydrochloride salt of sepiapterin formed in step (i);

(iii) neutralizing the hydrochloride salt of sepiapterin obtained in step (ii) with a base to obtain a crystalline form of sepiapterin.

In some embodiments, the method further includes (ii-1) combining the hydrochloride salt of sepiapterin isolated in step (ii) with hydrochloric acid and (ii-2) isolating the resulting hydrochloride salt of sepiapterin prior to carrying out step (iii). In some embodiments, the hydrochloric acid employed in step (i) is about 1N-6N in strength. In some embodiments, the base employed in step (iii) is an inorganic base (e.g., aqueous sodium hydroxide). In some embodiments, the hydrochloric acid employed in step (ii-1) is about 1N-6N in strength.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes dissolving sepiapterin free base in dimethyl acetamide, adding to the solution acetone, ethyl acetate, or THF, and isolating the solids to obtain the crystalline form of sepiapterin.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes dissolving sepiapterin free base in dimethyl sulfoxide, adding to the solution isopropyl alcohol, and cooling the solution to obtain the crystalline form of sepiapterin. In some embodiments, the solution is cooled to about −20° C.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes preparing a slurry of sepiapterin free base in methyl tert-butyl ether, n-heptane, toluene, a mixture of chloroform and n-heptane, or a mixture of acetone and methyl tert-butyl ether, stirring the resulting suspension, and isolating the solids to obtain the crystalline form of sepiapterin. In some embodiments, the suspension is stirred for 12-36 hours at 40-60° C.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes exposing sepiapterin free base to a vapor of water, methyl t-butyl ether, n-heptane, or toluene, and obtaining crystalline Form A of sepiapterin. In some embodiments, the sepiapterin free base is exposed to the vapor of water, methyl t-butyl ether, n-heptane, or toluene for 1-7 days at 10-40° C.

In another aspect, the invention features a method of preparing any of the foregoing crystalline forms of sepiapterin, this method includes dissolving sepiapterin free base in dimethyl acetamide and exposing the solution to a vapor of dichloromethane and obtaining the crystalline form of sepiapterin. In some embodiments, the sepiapterin free base is exposed to the vapor of dichloromethate for 1-7 days at 10-40° C.

In another aspect, the invention features a method for treating a BH4 related disorder in a patient in need thereof, the method comprising administering to the patient an effective amount of any of the foregoing crystalline forms of sepiapterin or pharmaceutical compositions. In some embodiments, the BH4-related disorder is a disease associated with low intracellular BH4 levels or with dysfunction of various BH4 dependent metabolic pathways including, but not limited to, primary tetrahydrobiopterin deficiency, GTPCH deficiency, 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency, DHPR deficiency, sepiapterin reductase deficiency, dopamine responsive dystonia, Segawa Syndrome, tyrosine hydroxylase deficiency, phenylketonuria, DNAJC12 deficiency, Parkinson's Disease, depression due to Parkinson's Disease, impulsivity in Parkinson's patients, major depression, Autism spectrum, ADHD, schizophrenia, Bipolar disorder, cerebral ischemia, restless leg syndrome, Obsessive Compulsive Disorder, anxiety, aggression in Alzheimer's disease, cerebrovascular disorders, spasm after subarachnoidal hemorrhage, myocarditis, coronary vasospasm, cardiac hypertrophy, arteriosclerosis, hypertension, thrombosis, infections, endotoxin shock, hepatic cirrhosis, hypertrophic pyloric stenosis, gastric mucosal injury, pulmonary hypertension, renal dysfunction, impotence, and hypoglycemia. Thus, the various forms of sepiapterin in accordance with the present invention can be administered to a patient in an effective amount to obtain a treatment or amelioration of the disease or dysfunction.

In another aspect, the invention features a method of increasing BH4, serotonin, and/or dopamine levels (e.g., at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 300%, 400%, 500%, 1000% or more) in a subject in need thereof, the method comprising administering to the patient an effective amount of any of the foregoing crystalline forms of sepiapterin or pharmaceutical compositions.

In another aspect, the invention features a method of decreasing phenylalanine levels (e.g., at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 300%, 400%, 500%, 1000% or more) in a subject in need thereof, the method comprising administering to the patient an effective amount of any of the foregoing crystalline forms of sepiapterin or a pharmaceutical compositions.

In another aspect, the invention features a method of increasing the activity (e.g., at least 55%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 300%, 400%, 500%, 1000% or more) of phenylalanine hydroxylase, tyrosine hydroxylase, tryptophan hydroxylase, nitric oxide synthase, and/or alkylglycerol monooxygenase in a subject, the method comprising administering to the patient an effective amount of any of the foregoing crystalline forms of sepiapterin or a pharmaceutical compositions.

In another aspect, the invention features a method of treating phenylketonuria in a subject in need thereof, the method comprising administering to the patient an effective amount of any of the foregoing crystalline forms of sepiapterin or pharmaceutical compositions.

Definitions

In this application, unless otherwise clear from context, (i) the term “a” may be understood to mean “at least one”; (ii) the term “or” may be understood to mean “and/or”; (iii) the terms “comprising” and “including” may be understood to encompass itemized components or steps whether presented by themselves or together with one or more additional components or steps; and (iv) the terms “about” and “approximately” may be understood to permit standard variation as would be understood by those of ordinary skill in the art; and (v) where ranges are provided, endpoints are included.

As used herein, the term “administration” refers to the administration of a composition (e.g., a compound or a preparation that includes a compound as described herein) to a subject or system. Administration to an animal subject (e.g., to a human) may be by any appropriate route. For example, in some embodiments, administration may be bronchial (including by bronchial instillation), buccal, enteral, interdermal, intra-arterial, intradermal, intragastric, intramedullary, intramuscular, intranasal, intraperitoneal, intrathecal, intravenous, intraventricular, mucosal, nasal, oral, rectal, subcutaneous, sublingual, topical, tracheal (including by intratracheal instillation), transdermal, vaginal and vitreal.

As used herein, the term “BH4 related disorder,” refers to any disease or disorder that may derive a therapeutic benefit from modulation (e.g., inhibition) of the level of BH4, e.g., phenylketonuria.

By “determining the level of a protein” is meant the detection of a protein, or an mRNA encoding the protein, by methods known in the art either directly or indirectly. “Directly determining” means performing a process (e.g., performing an assay or test on a sample or “analyzing a sample” as that term is defined herein) to obtain the physical entity or value. “Indirectly determining” refers to receiving the physical entity or value from another party or source (e.g., a third party laboratory that directly acquired the physical entity or value). Methods to measure protein level generally include, but are not limited to, western blotting, immunoblotting, enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), immunoprecipitation, immunofluorescence, surface plasmon resonance, chemiluminescence, fluorescent polarization, phosphorescence, immunohistochemical analysis, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, liquid chromatography (LC)-mass spectrometry, microcytometry, microscopy, fluorescence activated cell sorting (FACS), and flow cytometry, as well as assays based on a property of a protein including, but not limited to, enzymatic activity or interaction with other protein partners. Methods to measure mRNA levels are known in the art.

An “effective amount” of a compound may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the compound to elicit the desired response. A therapeutically effective amount encompasses an amount in which any toxic or detrimental effects of the compound are outweighed by the therapeutically beneficial effects. A therapeutically effective amount also encompasses an amount sufficient to confer benefit, e.g., clinical benefit.

By “increasing the activity of phenylalanine hydroxylase,” is meant increasing the level of an activity related to phenylalanine hydroxylase, or a related downstream effect. A non-limiting example of increasing an activity of phenylalanine hydroxylase is decreasing the level of phenylalanine. The activity level of phenylalanine hydroxylase may be measured using any method known in the art.

By “level” is meant a level of a protein, or mRNA encoding the protein, as compared to a reference. The reference can be any useful reference, as defined herein. By a “decreased level” or an “increased level” of a protein is meant a decrease or increase in protein level, as compared to a reference (e.g., a decrease or an increase by about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 100%, about 150%, about 200%, about 300%, about 400%, about 500%, or more; a decrease or an increase of more than about 10%, about 15%, about 20%, about 50%, about 75%, about 100%, or about 200%, as compared to a reference; a decrease or an increase by less than about 0.01-fold, about 0.02-fold, about 0.1-fold, about 0.3-fold, about 0.5-fold, about 0.8-fold, or less; or an increase by more than about 1.2-fold, about 1.4-fold, about 1.5-fold, about 1.8-fold, about 2.0-fold, about 3.0-fold, about 3.5-fold, about 4.5-fold, about 5.0-fold, about 10-fold, about 15-fold, about 20-fold, about 30-fold, about 40-fold, about 50-fold, about 100-fold, about 1000-fold, or more). A level of a protein may be expressed in mass/vol (e.g., g/dL, mg/mL, μg/mL, ng/mL) or percentage relative to total protein or mRNA in a sample.

The term “pharmaceutical composition,” as used herein, represents a composition containing a compound described herein formulated with a pharmaceutically acceptable excipient, and manufactured or sold with the approval of a governmental regulatory agency as part of a therapeutic regimen for the treatment of disease in a mammal. Pharmaceutical compositions can be formulated, for example, for oral administration in unit dosage form (e.g., a tablet, capsule, caplet, gelcap, or syrup); for topical administration (e.g., as a cream, gel, lotion, or ointment); for intravenous administration (e.g., as a sterile solution free of particulate emboli and in a solvent system suitable for intravenous use); or in any other pharmaceutically acceptable formulation.

A “pharmaceutically acceptable excipient,” as used herein, refers any ingredient other than the compounds described herein (for example, a vehicle capable of suspending or dissolving the active compound) and having the properties of being substantially nontoxic and non-inflammatory in a patient. Excipients may include, for example: antiadherents, antioxidants, binders, coatings, compression aids, disintegrants, dyes (colors), emollients, emulsifiers, fillers (diluents), film formers or coatings, flavors, fragrances, glidants (flow enhancers), lubricants, preservatives, printing inks, sorbents, suspensing or dispersing agents, sweeteners, and waters of hydration. Exemplary excipients include, but are not limited to: butylated hydroxytoluene (BHT), calcium carbonate, calcium phosphate (dibasic), calcium stearate, croscarmellose, crosslinked polyvinyl pyrrolidone, citric acid, crospovidone, cysteine, ethylcellulose, gelatin, hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, maltitol, mannitol, methionine, methylcellulose, methyl paraben, microcrystalline cellulose, polyethylene glycol, polyvinyl pyrrolidone, povidone, pregelatinized starch, propyl paraben, retinyl palmitate, shellac, silicon dioxide, sodium carboxymethyl cellulose, sodium citrate, sodium starch glycolate, sorbitol, starch (corn), stearic acid, sucrose, talc, titanium dioxide, vitamin A, vitamin E, vitamin C, and xylitol.

As used herein, the term “pharmaceutically acceptable salt” means any pharmaceutically acceptable salt of the compound of formula (I). For example, pharmaceutically acceptable salts of any of the compounds described herein include those that are within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and animals without undue toxicity, irritation, allergic response and are commensurate with a reasonable benefit/risk ratio. Pharmaceutically acceptable salts are well known in the art. For example, pharmaceutically acceptable salts are described in: Berge et al., J. Pharmaceutical Sciences 66:1-19, 1977 and in Pharmaceutical Salts: Properties, Selection, and Use, (Eds. P. H. Stahl and C. G. Wermuth), Wiley-VCH, 2008. The salts can be prepared in situ during the final isolation and purification of the compounds described herein or separately by reacting a free base group with a suitable organic acid.

The compounds of the invention may have ionizable groups so as to be capable of preparation as pharmaceutically acceptable salts. These salts may be acid addition salts involving inorganic or organic acids or the salts may, in the case of acidic forms of the compounds of the invention be prepared from inorganic or organic bases. Frequently, the compounds are prepared or used as pharmaceutically acceptable salts prepared as addition products of pharmaceutically acceptable acids or bases. Suitable pharmaceutically acceptable acids and bases and methods for preparation of the appropriate salts are well-known in the art. Salts may be prepared from pharmaceutically acceptable non-toxic acids and bases including inorganic and organic acids and bases.

Representative acid addition salts include acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptonate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, toluenesulfonate, undecanoate, and valerate salts. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, and magnesium, as well as nontoxic ammonium, quaternary ammonium, and amine cations, including, but not limited to ammonium, tetramethylammonium, tetraethylammonium, methylamine, dimethylamine, trimethylamine, triethylamine, and ethylamine.

By a “reference” is meant any useful reference used to compare protein or mRNA levels. The reference can be any sample, standard, standard curve, or level that is used for comparison purposes. The reference can be a normal reference sample or a reference standard or level. A “reference sample” can be, for example, a control, e.g., a predetermined negative control value such as a “normal control” or a prior sample taken from the same subject; a sample from a normal healthy subject, such as a normal cell or normal tissue; a sample (e.g., a cell or tissue) from a subject not having a disease; a sample from a subject that is diagnosed with a disease, but not yet treated with a compound of the invention; a sample from a subject that has been treated by a compound of the invention; or a sample of a purified protein (e.g., any described herein) at a known normal concentration. By “reference standard or level” is meant a value or number derived from a reference sample. A “normal control value” is a pre-determined value indicative of non-disease state, e.g., a value expected in a healthy control subject. Typically, a normal control value is expressed as a range (“between X and Y”), a high threshold (“no higher than X”), or a low threshold (“no lower than X”). A subject having a measured value within the normal control value for a particular biomarker is typically referred to as “within normal limits” for that biomarker. A normal reference standard or level can be a value or number derived from a normal subject not having a disease or disorder (e.g., cancer); a subject that has been treated with a compound of the invention. In preferred embodiments, the reference sample, standard, or level is matched to the sample subject sample by at least one of the following criteria: age, weight, sex, disease stage, and overall health. A standard curve of levels of a purified protein, e.g., any described herein, within the normal reference range can also be used as a reference.

As used herein, the term “subject” or “patient” refers to any organism to which a composition in accordance with the invention may be administered, e.g., for experimental, diagnostic, prophylactic, and/or therapeutic purposes. Typical subjects include any animal (e.g., mammals such as mice, rats, rabbits, non-human primates, and humans). A subject may seek or be in need of treatment, require treatment, be receiving treatment, be receiving treatment in the future, or be a human or animal who is under care by a trained professional for a particular disease or condition.

As used herein, the terms “treat,” “treated,” or “treating” mean both therapeutic treatment and prophylactic or preventative measures wherein the object is to prevent or slow down (lessen) an undesired physiological condition, disorder, or disease, or obtain beneficial or desired clinical results. Beneficial or desired clinical results include, but are not limited to, alleviation of symptoms; diminishment of the extent of a condition, disorder, or disease; stabilized (i.e., not worsening) state of condition, disorder, or disease; delay in onset or slowing of condition, disorder, or disease progression; amelioration of the condition, disorder, or disease state or remission (whether partial or total), whether detectable or undetectable; an amelioration of at least one measurable physical parameter, not necessarily discernible by the patient; or enhancement or improvement of condition, disorder, or disease. Treatment includes eliciting a clinically significant response without excessive levels of side effects. Treatment also includes prolonging survival as compared to expected survival if not receiving treatment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Methods and materials are described herein for use in the present disclosure; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

The details of one or more embodiments of the invention are set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 shows an overlay of the X-ray diffraction diagrams of the crystalline Form A of sepiapterin before and after a grinding and sieving process and confirms the physical stability of the polymorphic form to grinding and sieving.

FIG. 2 depicts the TGA and DSC curves of crystalline Form A of sepiapterin before grinding.

FIG. 3 depicts the TGA and DSC curves of crystalline Form A of sepiapterin after grinding.

FIG. 4 depicts the ¹H NMR of sepiapterin in solution.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In an embodiment, the invention provides a crystalline polymorph of sepiapterin herein referred to as the Form A.

The polymorphic Form A of sepiapterin may be characterized by any suitable method for studying solid state materials. In an embodiment, the polymorphic form is characterized by X-ray powder Diffractometry (XRPD). The XRPD peak positions are expressed as 2θ°. In the X-ray diagram, the angle of refraction 2θ is plotted on the horizontal axis (x-axis) and the relative peak intensity (background-corrected peak intensity) on the vertical (y-axis). X-ray powder diffraction patterns are obtained on, or using instruments comparable to, a PANalytical Empyrean X-ray powder diffractometer with Cu Kα radiation source (Kα1 radiation, wavelength Δ=1.54060 Angstrom, Kα2 radiation, wavelength 1.544426 Angstrom; Kα2/Kα1 intensity ratio: 0.50). The optical density of the peaks on the film is proportional to the light intensity. The film is scanned using a peak scanner.

As it relates to any of the peaks of X-ray powder diffraction set forth throughout this application, “about” refers to ±0.1, particularly ±0.05, and more particularly ±0.02 of the 2θ values in degrees.

In an embodiment, the crystalline polymorph Form A of sepiapterin is characterized by an X-ray powder diffraction pattern obtained by irradiation with Cu Kα X-rays having peaks expressed as 2θ at about 4.7°, about 7.4°, and about 26.2°.

In some embodiments, the crystalline polymorph Form A of sepiapterin has at least one peak at a diffraction angle 2θ (°) of 4.7°±0.5, 7.4°±0.5, 9.5°±0.5, 11.3°±0.5, 15.6°±0.5, 16.4°±0.5, 26.2°±0.5, or 27.2°±0.5.

In a particular embodiment, the crystalline polymorph Form A of sepiapterin is characterized by an X-ray powder diffraction pattern obtained by irradiation with Cu Kα X-rays having peaks expressed as 2θ at about 4.7°, about 7.4°, about 9.5°, about 11.3°, about 15.6°, about 16.4°, about 26.2°, and about 27.2°.

The crystalline Form A of sepiapterin free base is characterized by an X-ray powder diffraction pattern obtained by irradiation with Cu Kα X-rays having peaks expressed as 2θ at about 4.7°, about 7.4°, about 9.5°, about 11.3°, about 15.6°, about 16.4°, about 26.2°, and about 27.2°.

FIG. 1 shows the X-ray diffraction diagram of Form A of sepiapterin free base. The most intense peak in the X-ray diffraction diagram is observed at an angle of refraction 2θ of about 7.4°. The crystalline Form A is characterized by the 2θ peak positions of about 4.7°, about 7.4°, about 9.5°, about 11.3°, about 15.6°, about 26.2°, and about 27.2°. In an essentially pure material, crystal Form A of sepiapterin free base, peaks can be observed at angles of refraction 2θ as set forth in Table 1.

TABLE 1 XRPD peak positions of crystalline Form A of sepiapterin free base Position Relative [°2θ] Intensity 4.741367 47.76 7.352421 100.00 9.521946 33.54 11.330880 19.31 12.388140 8.49 13.365340 3.60 14.170660 8.24 15.569500 15.08 16.381160 11.97 17.638530 8.35 18.418820 5.03 19.780530 9.18 21.528770 5.44 24.353510 5.56 26.244710 35.37 27.248910 19.11 28.871850 5.93

In the context of stating that crystalline Form A of sepiapterin free base exhibits an X-ray diffraction diagram essentially as in FIG. 1, the term “essentially” means that at least the major peaks of the diagram depicted in FIG. 1, i.e., those having a relative peak intensity of more than 20%, especially more than 30%, as compared to the most intense peak in the diagram, have to be present. Alternatively, or in addition, crystalline Form A of sepiapterin free base is characterized by a DSC curve showing endothermal peaks at 82.8° C. and 179.8° C.

TGA and DSC data of crystalline Form A before grinding are displayed in FIG. 2. A weight loss of 5.3% was observed up to 150° C. on TGA. The DSC result showed two endotherms at 82.8 and 179.8° C. (peak temperature). The starting material contained large particles with size over 100 μm. It was ground and characterized by XRPD, TGA and DSC. The XRPD pattern shown in FIG. 1 indicates that no form change was observed after grinding. TGA and DSC curves of the material after grinding are displayed in FIG. 3. A weight loss of 1.9% was observed after N2 purging for 30 min to remove the absorbed water, followed by a second-step weight loss of 13.7% from 30° C. to 150° C. on TGA. The DSC result showed two endotherms at 85.9° C. and 179.7° C. (peak temperature).

In any of the above embodiments, the crystalline sepiapterin free base can occur as an anhydrate (e.g., without having any bound water or hydration) or as a hydrate, a partial hydrate (e.g., hemihydrate, sesquihydrate, and the like), as a dihydrate, a trihydrate, or the like, wherein the crystalline form binds a water of hydration associated with the crystalline form of sepiapterin. In an embodiment, crystalline sepiapterin Form A occurs as a dihydrate.

In any of the above embodiments, the crystalline sepiapterin free base can occur as a solvate or as a solvate of an anhydrate (e.g., without having any bound water) or as a solvate of a hydrate (e.g., hemihydrate, sesquihydrate, and the like), as a solvate of a dihydrate, a solvate of a trihydrate, or the like, wherein the crystalline form binds a water of hydration associated with the crystalline form of sepiapterin. In some instances, solvates may be formed with acetone, ethyl acetate, tetrahydrofuran, 2-methyl tetrahydrofuran, dichloromethane, 1,4-dioxane, methyl tert-butyl ether, n-heptane, toluene, chloroform or isopropyl alcohol.

In an embodiment, the invention provides a method for preparing crystalline Form A of sepiapterin. The starting material is a crude sepiapterin, which can be prepared by any suitable method, for example, as disclosed in U.S. Pat. No. 9,181,254, the method of which is incorporated herein in its entirety for all purposes. Thus, for example, sepiapterin can be prepared from S-lactoylpterin by subjecting it to reduction, for example, by the use of a sulfite, a hyposulfite or a thiosulfate, or a BH3-based reducing agent, or by catalytic reduction under basic conditions. Alternatively, sepiapterin can be prepared by oxidizing tetrahydrolactoylpterin by the use of a peracid, or by air oxidation under neutral or basic conditions. Other methods of preparing sepiapterin include those disclosed in Pfleiderer, Sugiura et al., and Schircks et al., the methods of which are incorporated by reference.

FIG. 4 depicts the ¹H NMR of sepiapterin in solution.

The approximate solubility of starting material was measured at RT as set forth in Table 2.

TABLE 2 Approximate solubility of starting material Solubility Solubility Solvent (mg/mL) Solvent (mg/mL) MeOH  1.7 < S < 3.4 1,4-Dioxane S < 1.7 EtOH S < 1.5 ACN S < 1.7 IPA S < 1.3 DCM S < 1.5 Acetone S < 1.8 CHCl₃ S < 1.6 MIBK S < 2.0 n-Heptane S < 2.1 EtOAc S < 2.5 Toluene S < 2.4 IPAc S < 2.7 DMAc  S > 28.0 MTBE S < 2.0 DMSO  S > 34.0 THF S < 1.9 NMP  S > 48.0 2-MeTHF S < 2.0 H₂O   1.6 < S < 3.2

In accordance with the present invention, the method for preparing crystalline Form A of sepiapterin comprises (i) combining sepiapterin free base, for example, a crude sample of sepiapterin free base, and hydrochloric acid; (ii) isolating the hydrochloride salt of sepiapterin formed in step (i); and (iii) neutralizing the hydrochloride salt of sepiapterin obtained in step (ii) with a base to obtain crystalline Form A of sepiapterin.

In a particular embodiment, the method further comprises the steps of: (ii-1) combining the hydrochloride salt of sepiapterin separated in step (ii) with hydrochloric acid and (ii-2) separating the resulting hydrochloride salt of sepiapterin prior to carrying out step (iii). In some embodiments, the method further includes washing the solids with water prior to neutralization with a base in step (iii).

In an embodiment, the hydrochloric acid employed in step (i) is about 1N-6N in strength. The step of combining crude sepiapterin with hydrochloric acid is carried out at below room temperature, e.g., below 20° C., below 10° C., and preferably between 0° C. to 10° C. The mixture is stirred for a suitable period, for example 1-30 minutes, 1-20 minutes, or 1-10 minutes, and the mixture is stirred at a temperature 0 to 10° C. The resulting solids are isolated, e.g., by filtration. The isolated solids are washed with ethanol. The solids are added to cold water, e.g., at a temperature of 0 to 10° C. and stirred. The solids are filtered and neutralized to pH 7 in an aqueous environment with a base and cooled, e.g., to below 10° C. In an embodiment, the base employed in step (iii) is an inorganic base, e.g., aqueous sodium hydroxide. The strength of the base can be any suitable strength, e.g., about 0.1N to about 10N.

In an embodiment, a further treatment of the solids obtained in step (ii) are further combined with hydrochloric acid in step (ii-1). The strength of the hydrochloric acid in step (ii-1) can be about 1N-6N. In an embodiment, the resulting solids are filtered and washed with water, e.g., at a temperature of 0 to 10° C. and step (iii) is performed by mixing the hydrochloride salt of sepiapterin from step (ii-2) in water prior to neutralizing the hydrochloride salt of sepiapterin with a base.

The resulting solids are dried, e.g., at a temperature of 20° C. to 60° C., preferably at about 40° C., to obtain crystalline Form A of sepiapterin.

The invention further provides a method of preparing a crystalline sepiapterin of Form A comprising dissolving sepiapterin free base in dimethyl acetamide, adding to the solution acetone, ethyl acetate, or THF, and isolating the solids to obtain crystalline Form A of sepiapterin.

The invention further provides a method of preparing a crystalline sepiapterin of Form A comprising dissolving sepiapterin free base in dimethyl sulfoxide, adding to the solution isopropyl alcohol and cooling, e.g., to about −20° C. to obtain crystalline Form A of sepiapterin.

The invention further provides a method of preparing crystalline sepiapterin of Form A comprising preparing a slurry of sepiapterin free base in methyl tert-butyl ether, n-heptane, toluene, a mixture of chloroform and n-heptane, or a mixture of acetone and methyl tert-butyl ether, stirring the resulting suspension, e.g., for 12-36 hrs at 40-60° C. temperature, and isolating the solids to obtain crystalline Form A of sepiapterin.

The invention further provides a method of preparing a crystalline Form A of sepiapterin comprising exposing, e.g., at 10-40° C. for 1-7 days, sepiapterin to a vapor of water, methyl t-butyl ether, n-heptane, or toluene and obtaining crystalline Form A of sepiapterin.

The invention further provides a method of preparing a crystalline Form A of sepiapterin comprising dissolving sepiapterin in dimethyl acetamide and exposing the solution, e.g., at 10-40° C. for 1-7 days, to a vapor of dichloromethane and obtaining crystalline Form A of sepiapterin.

Crystalline Form A of sepiapterin may serve as a useful therapeutic for BH4-related disorders. In some embodiments, the BH4-related disorder is a disease associated with low intracellular BH4 levels or with dysfunction of various BH4 dependent metabolic pathways including, but not limited to, primary tetrahydrobiopterin deficiency, GTPCH deficiency, 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency, DHPR deficiency, sepiapterin reductase deficiency, dopamine responsive dystonia, Segawa Syndrome, tyrosine hydroxylase deficiency, phenylketonuria, DNAJC12 deficiency, Parkinson's Disease, depression due to Parkinson's Disease, impulsivity in Parkinson's patients, major depression, Autism spectrum, ADHD, schizophrenia, Bipolar disorder, cerebral ischemia, restless leg syndrome, Obsessive Compulsive Disorder, anxiety, aggression in Alzheimer's disease, cerebrovascular disorders, spasm after subarachnoidal hemorrhage, myocarditis, coronary vasospasm, cardiac hypertrophy, arteriosclerosis, hypertension, thrombosis, infections, endotoxin shock, hepatic cirrhosis, hypertrophic pyloric stenosis, gastric mucosal injury, pulmonary hypertension, renal dysfunction, impotence, and hypoglycemia. Thus, the various forms of sepiapterin in accordance with the present invention can be administered to a patient in an effective amount to obtain a treatment or amelioration of the disease or dysfunction.

An “effective amount” of a compound may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the compound to elicit the desired response. A therapeutically effective amount encompasses an amount in which any toxic or detrimental effects of the compound are outweighed by the therapeutically beneficial effects. A therapeutically effective amount also encompasses an amount sufficient to confer benefit, e.g., clinical benefit.

The present invention further provides a pharmaceutical composition comprising a crystalline Form A of sepiapterin as described above and a pharmaceutically acceptable carrier. The present invention provides a pharmaceutical composition comprising a pharmaceutically acceptable carrier and an effective amount, e.g., a therapeutically effective amount, including a prophylactically effective amount, of crystalline Form A of sepiapterin.

The pharmaceutically acceptable carrier can be any of those conventionally used and is limited only by chemico-physical considerations, such as lack of solubility or reactivity with the compound, and by the route of administration. It will be appreciated by one of skill in the art that, in addition to the following described pharmaceutical compositions; the compound of the present invention can be formulated as inclusion complexes, such as cyclodextrin inclusion complexes, or liposomes.

The pharmaceutically acceptable carriers described herein, for example, vehicles, adjuvants, excipients, or diluents, are well known to those who are skilled in the art and are readily available to the public. It is preferred that the pharmaceutically acceptable carrier be one which is chemically inert to the active compounds and one which has no detrimental side effects or toxicity under the conditions of use.

The choice of carrier will be determined in part by the particular active agent, as well as by the particular method used to administer the composition. Accordingly, there is a wide variety of suitable formulations of the pharmaceutical composition of the present invention. The following formulations for oral, aerosol, parenteral, subcutaneous, intramuscular, intraperitoneal, rectal, and vaginal administration are merely exemplary and are in no way limiting.

The crystalline Form A of sepiapterin can be used in the preparation of liquid formulations, such as in the form of a suspension or emulsion. Formulations suitable for oral administration can consist of (a) capsules, sachets, tablets, lozenges, and troches, each containing a predetermined amount of the active ingredient, as solids or granules; (b) powders; (c) liquid suspensions, such as an effective amount of the compound suspended in diluents, such as water, saline, or orange juice; (d) suspensions in an appropriate liquid; and (e) suitable emulsions. Preferred are solid oral dosage forms such as capsule forms, tablet forms, and powder forms. Capsule forms can be of the ordinary hard- or soft-shelled gelatin type containing, for example, surfactants, lubricants, and inert fillers, such as lactose, sucrose, calcium phosphate, and cornstarch. Tablet forms can include one or more of lactose, sucrose, mannitol, corn starch, potato starch, alginic acid, microcrystalline cellulose, acacia, gelatin, guar gum, colloidal silicon dioxide, croscarmellose sodium, talc, magnesium stearate, calcium stearate, zinc stearate, stearic acid, and other excipients, colorants, diluents, buffering agents, disintegrating agents, moistening agents, preservatives, flavoring agents, and pharmacologically compatible carriers. Lozenge forms can comprise the active ingredient in a flavor, usually sucrose and acacia or tragacanth, as well as pastilles comprising the active ingredient in an inert base, such as gelatin and glycerin, or sucrose and acacia, emulsions, gels, and the like containing, in addition to the active ingredient, such carriers as are known in the art.

Formulations suitable for oral and/or parenteral administration include aqueous and non-aqueous, isotonic sterile injection suspensions, which can contain anti-oxidants, buffers, bacteriostats, and solutes that render the formulation isotonic with the blood of the intended recipient, and aqueous and non-aqueous sterile suspensions that can include suspending agents, solubilizers, thickening agents, stabilizers, and preservatives. The compound can be administered in a physiologically acceptable diluent in a pharmaceutical carrier, such as a sterile liquid or mixture of liquids, including water, saline, aqueous dextrose and related sugar solutions, an alcohol, such as ethanol, benzyl alcohol, or hexadecyl alcohol, glycols, such as propylene glycol or polyethylene glycol and other polyethylene alcohols, glycerol ketals, such as 2,2-dimethyl-1,3-dioxolane-4-methanol, ethers, such as poly(ethylene glycol) 400, an oil, a fatty acid, a fatty acid ester or glyceride, or an acetylated fatty acid glyceride with or without the addition of a pharmaceutically acceptable surfactant, such as a soap or a detergent, suspending agent, such as pectin, carbomers, methylcellulose, hydroxypropylmethylcellulose, or carboxymethylcellulose, or emulsifying agents and other pharmaceutical adjuvants.

Oils, which can be used in parenteral formulations include petroleum, animal, vegetable, or synthetic oils. Specific examples of oils include peanut, soybean, sesame, cottonseed, corn, olive, petrolatum, and mineral. Suitable fatty acids for use in parenteral formulations include oleic acid, stearic acid, and isostearic acid. Ethyl oleate and isopropyl myristate are examples of suitable fatty acid esters. Suitable soaps for use in parenteral formulations include fatty alkali metal, ammonium, and triethanolamine salts, and suitable detergents include (a) cationic detergents such as, for example, dimethyl dialkyl ammonium halides, and alkyl pyridinium halides, (b) anionic detergents such as, for example, alkyl, aryl, and olefin sulfonates, alkyl, olefin, ether, and monoglyceride sulfates, and sulfosuccinates, (c) nonionic detergents such as, for example, fatty amine oxides, fatty acid alkanolamides, and polyoxyethylene-polypropylene copolymers, (d) amphoteric detergents such as, for example, alkyl-beta-aminopropionates, and 2-alkyl-imidazo quaternary ammonium salts, and (3) mixtures thereof.

The parenteral formulations typically contain from about 0.5 to about 25%, about 30%, about 35%, about 40%, or more, by weight of the crystalline Form A of sepiapterin in suspension. Suitable preservatives and buffers can be used in such formulations. In order to minimize or eliminate irritation at the site of injection, such compositions may contain one or more nonionic surfactants having a hydrophilic-lipophilic balance (HLB) of from about 12 to about 17. The quantity of surfactant in such formulations ranges from about 5 to about 15% by weight. Suitable surfactants include polyethylene sorbitan fatty acid esters, such as sorbitan monooleate and the high molecular weight adducts of ethylene oxide with a hydrophobic base, formed by the condensation of propylene oxide with propylene glycol. The parenteral formulations can be presented in unit-dose or multi-dose sealed containers, such as ampoules and vials, and can be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example, water, for injections, immediately prior to use. Extemporaneous injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described.

The crystalline Form A of sepiapterin of the present invention may be made into injectable formulations. The requirements for effective pharmaceutical carriers for injectable compositions are well known to those of ordinary skill in the art. See Pharmaceutics and Pharmacy Practice, J. B. Lippincott Co., Philadelphia, Pa., Banker and Chalmers, eds., pages 238-250 (1982), and ASHP Handbook on Injectable Drugs, Toissel, 4th ed., pages 622-630 (1986).

Topical formulations, including those that are useful for transdermal drug release, are well-known to those of skill in the art and are suitable in the context of the invention for application to skin. Topically applied compositions are generally in the form of liquids, creams, pastes, lotions and gels. Topical administration includes application to the oral mucosa, which includes the oral cavity, oral epithelium, palate, gingival, and the nasal mucosa. In some embodiments, the composition contains at least crystalline Form A of sepiapterin and a suitable vehicle or carrier. It may also contain other components, such as an anti-irritant. The carrier can be a liquid, solid or semi-solid. In embodiments, the composition is an aqueous solution. Alternatively, the composition can be a dispersion, emulsion, gel, lotion or cream vehicle for the various components. In one embodiment, the primary vehicle is water or a biocompatible solvent that is substantially neutral or that has been rendered substantially neutral. The liquid vehicle can include other materials, such as buffers, alcohols, glycerin, and mineral oils with various emulsifiers or dispersing agents as known in the art to obtain the desired pH, consistency and viscosity. It is possible that the compositions can be produced as solids, such as powders or granules. The solids can be applied directly or dissolved in water or a biocompatible solvent prior to use to form a solution that is substantially neutral or that has been rendered substantially neutral and that can then be applied to the target site. In embodiments of the invention, the vehicle for topical application to the skin can include water, buffered solutions, various alcohols, glycols such as glycerin, lipid materials such as fatty acids, mineral oils, phosphoglycerides, collagen, gelatin and silicone based materials.

The crystalline Form A of sepiapterin of the present invention, alone or in combination with other suitable components, can be made into aerosol formulations to be administered via inhalation. These aerosol formulations can be placed into pressurized acceptable propellants, such as dichlorodifluoromethane, propane, nitrogen, and the like. They also may be formulated as pharmaceuticals for non-pressured preparations, such as in a nebulizer or an atomizer.

Additionally, the crystalline Form A of sepiapterin of the present invention may be made into suppositories by mixing with a variety of bases, such as emulsifying bases or water-soluble bases. Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams, or spray formulas containing, in addition to the active ingredient, such carriers as are known in the art to be appropriate.

The crystalline Form A of sepiapterin can be used in any suitable dose. Suitable doses and dosage regimens can be determined by conventional range finding techniques. Generally, treatment is initiated with smaller dosages, which are less than the optimum dose. Thereafter, the dosage is increased by small increments until optimum effect under the circumstances is reached. For convenience, the total daily dosage may be divided and administered in portions during the day if desired.

In proper doses and with suitable administration of certain compounds, the present invention provides for a wide range of responses. Typically, the dosages range from about 0.001 to about 1000 mg/kg body weight of the patient being treated/day. For example, in embodiments, the crystalline Form A of sepiapterin may be administered from about 100 mg/kg to about 300 mg/kg, from about 120 mg/kg to about 280 mg/kg, from about 140 mg/kg to about 260 mg/kg, from about 150 mg/kg to about 250 mg/kg, from about 160 mg/kg to about 240 mg/kg, of subject body weight per day, one or more times a day, to obtain the desired therapeutic effect.

In some embodiments, the crystalline Form A of sepiapterin can be formulated into unit solid oral dosage forms such as powder, capsules, or tablets. In these embodiments, each unit solid oral dosage form can comprise any suitable amount of the crystalline Form A of sepiapterin. For example, each solid oral dosage form can comprise about 10 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg, about 100 mg, about 125 mg, about 150 mg, about 175 mg, about 200 mg, about 225 mg, about 250 mg, about 275 mg, about 300 mg, about 325 mg, about 350 mg, about 375 mg, about 400 mg, about 425 mg, about 450 mg, about 475 mg, about 50 mg, about 525 mg, about 550 mg, about 575 mg, about 600 mg, about 625 mg, about 650 mg, about 675 mg, about 700 mg, about 725 mg, about 750 mg, about 775 mg, about 800 mg, about 825 mg, about 850 mg, about 875 mg, about 900 mg, about 925 mg, about 950 mg, about 975 mg, about 1000 mg, about 2000 mg, about 3000 mg, about 4000 mg, about 5000 mg, and the like.

For X-ray powder diffraction analysis, a PANalytical™ Empyrean X-ray powder diffractometer was used. The XRPD parameters are as follows:

XRPD Parameters

Parameter Value X-Ray wavelength Cu, ka, Ka1 (Å): 1.540598, Ka2 (Å): 1.544426 Ka2/Ka1 intensity ratio: 0.50 X-Ray tube setting 45 kV, 40 mA Divergence slit Automatic Scan mode Continuous Scan range (°2θ) 3°~40° Scan step time (s) 17.8 Test time (s) 5 min 30 s

DSC was performed using a TA Q200/Q2000 DSC from TA Instruments. Parameters used are as follows:

Parameters DSC Method Ramp Sample pan Aluminum, crimped Temperature 25° C.-desired temperature Heating rate 10° C./min Purge gas N₂

EXAMPLES

While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. As such, the following examples are provided to teach various aspects of the present invention. These examples represent individual embodiments of the aspects of this invention and one skilled in the art will recognize that additional examples can be generated in order to equally teach the aspects of the present invention.

Example 1

This example demonstrates a preparation of the crystalline Form A of sepiapterin in accordance with an embodiment of the invention.

50.49 g of crude sepiapterin free base was added to 434 mL of 6N aqueous hydrochloric acid which had been cooled to 0° C. The mixture was stirred 0-10° C. for 30 minutes. The resulting solids were isolated by filtration and washed with ethanol. The solids were added to 434 mL of 1N aqueous hydrochloric acid already cooled to 0° C. and the mixture was stirred at 0-10° C. for 30 min. The resulting solids were isolated by filtration and washed with ethanol. The solids were added to 651 mL of water cooled to 0° C. The pH was adjusted to 7 by employing aqueous sodium hydroxide solution. The resulting solids were isolated by filtration and washed with water. The isolated solids were dried under vacuum at 40° C. to obtain crystalline Form A of sepiapterin.

Example 2

This example demonstrates a preparation of the crystalline Form A of sepiapterin in accordance with another embodiment of the invention.

274 g of crude sepiapterin free base was added to 2740 mL of 6N aqueous hydrochloric acid which had been cooled to 0° C. The mixture was stirred at 0-10° C. for 30 minutes. The resulting solids were isolated by filtration and washed with ethanol. The solids were added to 2740 mL of 6N aqueous hydrochloric acid already cooled to 0° C. and the mixture was stirred at 0-10° C. for 30 min. The resulting solids were isolated by filtration and washed with ethanol. The solids were added to 4100 mL of water cooled to 0° C. The pH was adjusted to 7 by employing aqueous sodium hydroxide solution. The resulting solids were isolated by filtration and washed with water. The isolated solids were dried under vacuum at 40° C. to obtain crystalline Form A of sepiapterin.

Example 3

This example demonstrates a preparation of the crystalline Form A of sepiapterin in accordance with yet another embodiment of the invention.

1.63 kg of crude sepiapterin free base was added to 13 L of 6N aqueous hydrochloric acid which had been cooled to 0° C. The mixture was stirred at 0-10° C. for 30 minutes. The resulting solids were isolated by filtration and washed with ethanol. The solids were added to 21 L of water cooled to 0° C. The pH was adjusted to 7 by employing aqueous sodium hydroxide solution. The resulting solids were isolated by filtration and washed with water. The isolated solids were dried under vacuum at 40° C. to obtain crystalline Form A of sepiapterin.

Example 4

This example demonstrates the stability of the crystalline Form A of sepiapterin.

Crystalline form A of sepiapterin of the invention was subjected to grinding and sieving process comprising grinding with a mortar and pestle and passing the material through a 140 mesh sieve. Material that did not pass through the sieve was further ground with a mortar and pestle and then passed through the 140 mesh sieve. This process was repeated until all material was passed through the sieve. X-ray diffraction revealed that the crystalline Form A was stable to the grinding and sieving process.

Example 5

This example demonstrates the preparation of crystalline Form A of sepiapterin free base via anti-solvent addition in accordance with an embodiment of the invention.

About 12 mg of sepiapterin free base was dissolved in 0.4 mL of a solvent to obtain a clear solution, and the solution was magnetically stirred followed by addition of 0.1 mL of an anti-solvent step by step until a precipitate appeared or the total amount of anti-solvent reached 10.0 mL. The precipitate obtained was isolated and characterized by XRPD. The clear solutions were transferred to stir at 5° C. or −20° C., and solids were isolated and tested by XRPD. The results showed that when the solvent was N,N-dimethyl acetamide and the anti-solvent was acetone, ethyl acetate, or tetrahydrofuran, crystalline Form A of sepiapterin was produced.

Example 6

This example demonstrates the preparation of crystalline Form A of sepiapterin free base via slurry conversion in accordance with an embodiment of the invention.

About 12 mg of starting material sepiapterin free base was suspended in 0.3 mL of a liquid in a 1.5-mL glass vial. After the suspension was stirred for 24 hrs at 50° C., the remaining solids were isolated and characterized by XRPD. The results obtained indicate that when the liquid was methyl tert-butyl ether, n-heptane, toluene, a mixture of chloroform and n-heptane (1:1 v/v), or a mixture of acetone and methyl tert-butyl ether (1:1 v/v) crystalline Form A of sepiapterin was produced.

Example 7

This example demonstrates the preparation of crystalline Form A of sepiapterin free base via solvent vapor diffusion in accordance with an embodiment of the invention.

Approximately 12 mg of starting material sepiapterin free base was weighed into a 3-mL vial, which was placed into a 20-mL vial with 4 mL of a volatile solvent. The 20-mL vial was sealed with a cap and kept at RT for 7 days allowing sufficient time for the solvent vapor to interact with the sample. The solids obtained were tested by XRPD and the results obtained showed that when the solvent was water, methyl tert-butyl ether (MTBE), 2-methyl THF, n-heptane, or toluene, crystalline Form A of sepiapterin was produced.

Example 8

This example demonstrates the preparation of crystalline Form A sepiapterin free base via liquid vapor diffusion in accordance with an embodiment of the invention.

Approximate 12 mg of starting material sepiapterin free base was dissolved in 0.3 mL of a solvent to obtain a clear solution in a 3-mL vial. This solution was placed into a 20-mL vial with 4 mL of a volatile anti-solvent. The 20-mL vial was sealed with a cap and kept at RT for 7 days allowing sufficient time for organic vapor from the anti-solvent to interact with the solution. The precipitates obtained were characterized by XRPD analysis. The results obtained showed that when the solvent was DMAc and the anti-solvent was dichloromethane, crystalline Form A was produced.

Other Embodiments

The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 

What is claimed: 1-37. (canceled)
 38. A crystalline form of the hydrochloride salt of sepiapterin having peaks at diffraction angle 2θ (°) of 7.8°±0.5, 12.9°±0.5, and 26.2°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry.
 39. The crystalline form of the hydrochloride salt of sepiapterin of claim 38 having peaks at diffraction angle 2θ (°) of 7.8°±0.5, 12.9°±0.5, 17.9°±0.5, 21.1°±0.5, 23.6°±0.5, 25.2°±0.5, 26.2°±0.5, 27.6°±0.5, and 30.3°±0.5 as measured by X-ray diffractometry by irradiation with Cu Kα X-rays or calculated from X-ray diffractometry.
 40. The crystalline form of the hydrochloride salt of sepiapterin of claim 38 having the X-Ray powder diffraction spectrum as shown in FIG.
 10. 41. The crystalline form of the hydrochloride salt of claim 38 having an endotherm at 225.9° C. in differential scanning calorimetry (DSC) profile.
 42. A pharmaceutical composition comprising the crystalline form of the hydrochloride salt of sepiapterin of claim 38 and a pharmaceutically acceptable carrier.
 43. The pharmaceutical composition of claim 42, wherein the crystalline form of the hydrochloride salt of sepiapterin is present in an amount of at least 90 percent by weight of the composition.
 44. The pharmaceutical composition of claim 42, wherein the crystalline form of the hydrochloride salt of sepiapterin is formulated as particles less than 100 μm in size.
 45. A method of preparing the crystalline form of the hydrochloride salt of sepiapterin of claim 38 comprising: (1) preparing a slurry of a first crystalline form of sepiapterin in acetone/water, adding hydrochloric acid, stirring the resulting suspension, and isolating the resulting solids; and (2) dispersing the solids obtained in step (1) in acetone/HCl, adding hydrochloric acid, and isolating the resulting solids.
 46. The method of claim 45, wherein the solids resulting from step (2) are isolated by vacuum filtration.
 47. The method of claim 45, wherein the solids resulting from step (2) are dried in vacuum.
 48. The method of claim 47, wherein the solids are dried overnight at room temperature.
 49. A method of treating primary tetrahydrobiopterin deficiency in a patient in need thereof, the method comprising administering to the patient an effective amount of the crystalline form of the hydrochloride salt of sepiapterin of claim
 38. 50. A method of decreasing phenylalanine levels in a patient in need thereof, the method comprising administering to the patient an effective amount of the crystalline form of the hydrochloride salt of sepiapterin of claim
 38. 51. A method of treating phenylketonuria in a patient in need thereof, the method comprising administering to the patient an effective amount of the crystalline form of the hydrochloride salt of sepiapterin of claim
 38. 